This invention relates to a tinted, green colored soda-lime-silica glass having a low luminous transmittance that makes it highly desirable for use as a privacy glazing in vehicles, such as the side and rear windows in vans. In particular, the glass has a luminous transmittance of 60% or less, preferably between about 10 to 40%. As used herein, the term xe2x80x9cgreen coloredxe2x80x9d is meant to include glasses that have a dominant wavelength of about 480 to 565 nanometers (nm) and may be characterized as green blue, green yellow or green gray in color. In addition, the glass of the present invention generally exhibits lower infrared and ultraviolet radiation transmittance when compared to typical green glasses used in automotive applications. The glass is also compatible with float glass manufacturing methods.
Various dark tinted, infrared and ultraviolet radiation absorbing glass compositions are known in the art. The primary colorant in typical dark tinted automotive privacy glasses is iron, which is usually present in both the Fe2O3 and FeO forms. Some glasses use cobalt, selenium and, optionally, nickel in combination with iron to further control infrared and ultraviolet radiation and color, for example as disclosed in U.S. Pat. No. 4,873,206 to Jones; U.S. Pat. No. 5,278,108 to Cheng et al.; U.S. Pat. No. 5,308,805 to Baker et al.; and U.S. Pat. No. 5,393,593 to Gulotta et al., and European Patent application EP 0 705 800. Others also include chromium with this combination of colorants as disclosed in U.S. Pat. No. 4,104,076 to Pons; U.S. Pat. No. 4,339,541 to Dela Ruye; U.S. Pat. No. 5,023,210 to Krumwiede et al; and U.S. Pat. No. 5,352,640 to Combes et al.; European Patent application EP 0 536 049; French Patent 2,331,527 and Canadian Patent 2,148,954. Still, other glasses may include additional materials, such as disclosed in WO 96/00194, which teaches the inclusion of fluorine, zirconium, zinc, cerium, titanium and copper in the glass composition and requires that the sum of the alkaline earth oxides be less than 10 wt. % of the glass.
In producing infrared and ultraviolet radiation absorbing glasses, the relative amounts of iron and other additives must be closely monitored and controlled within an operating range to provide the desired color and spectral properties. It would be desirable to have a dark tinted green colored glass that may be used as a privacy glazing for vehicles to complement the green colored glasses typically used in automobiles that exhibits superior solar performance properties and is compatible with commercial float glass manufacturing techniques.
The present invention provides a green colored, infrared and ultraviolet absorbing glass article having a luminous transmittance of up to 60 percent. The composition of the glass article uses a standard soda-lime-silica glass base composition and additionally iron, cobalt, selenium, and chromium, and optionally titanium, as infrared and ultraviolet radiation absorbing materials and colorants. The glasses of the present invention have a color characterized by a dominant wavelength in the range of about 480 to 565 nanometers, preferably about 495 to 560 nanometers, with an excitation purity of no higher than about 20%, preferably no higher than about 10%, and more preferably no higher than about 7%. The glass compositions may be provided with different levels of spectral performance depending on the particular application and desired luminous transmittance.
In one embodiment of the invention, the glass composition of a green colored, infrared and ultraviolet radiation absorbing soda-lime-silica glass article includes a solar radiation absorbing and colorant portion having about 0.60 to 4 percent by weight total iron, about 0.13 to 0.9 percent by weight FeO, about 40 to 500 PPM CoO, about 5 to 70 PPM Se, about 15 to 800 PPM Cr2O3, and about 0.02 to 1 percent by weight TiO2. In another embodiment of the invention, the glass composition of the article includes a solar radiation absorbing and colorant portion having 1 to less than 1.4 percent by weight total iron, about 0.2 to 0.6 percent by weight FeO, greater than 200 to about 500 PPM CoO, about 5 to 70 PPM Se, greater than 200 to about 800 PPM Cr2O3, and 0 to about 1 percent by weight TiO2.